Blood pressure-lowering agents available include, inter alia, diuretics, vasodilators, symphatholytics, calcium antagonists, as well as conversion enzyme inhibitors. These agents act through different mechanisms and, depending upon the severity and the spectrum of the underlying disease, in some cases incompatibilities may arise and the agents cause undesirable side effects. As a result, not only may it prove necessary for a physician to discontinue a course of treatment, but it is also known for a patient to discontinue his treatment as a result of his becoming aware of certain side effects.
Accordingly, there is a requirement for an effective treatment for hypertension having a lower incidence rate of side effects such as pathological blood pressure increase, increased heart rate and ischaemic heart disease.
The indole alkaloids ervatamine (J. S. Glasby, Encyclopedia of the Alkaloids, Vol. 1. (1975) and methuenine (P. Bakana, R. Dommisse, E. Esmans, R. Fokkens, J. Totte, N. M. N. Nibbering and A. J. Vlietinck, Planta Medica, 51, 331/1984), both of which substances have a chemical structure which is similar to that of acylindoles, are known in the art. However, these substances are not known as blood pressure lowering agents or as causative agents of bradycardia.